The Flow Cytometry Shared Resource offers Cancer Center users multi-parametric evaluation and high speed enrichment of phenotypically distinct cell populations using flow cytometry. For analytical flow cytometry, investigators have a choice of full-service analysis, or receiving training and then independent use of the two analytical flow cytometers (BD FACSort and BD FACSCanto). Investigator training and consulting is also provided on analytical software including CellQuest, FlowJo, and ModFitLT. For high-speed cell sorting, the facility provides experimental planning and full-service cell sorting by an expert operator, utilizing a BD FACSVantageSE DiVa. This instrument was recently equipped with a custom biosafety cabinet to enable sorting of cells infected with viral vectors, better protecting both the operator and the samples. The experienced Facility Director, Mr. Altman, provides investigators with extensive flow cytometry guidance, from experimental set-up, selection of reagents, setting gating or sorting parameters, data interpretation, and development of new methods. In the previous funding period. Flow Cytometry (previously the major part of the High Throughput Cell Analysis Shared Resource) performed key experiments described in at least 83 publications form Cancer Center members. The Resource is widely used, as in the past year, services were provided for 32 Cancer Center members, representing all four Programs. Plans for future development of the Resource include upgrading the current Flow Cytometers, and acquisition of a low-speed microfluidic sorter that can sort much lower numbers of cells and apply substantially lower shear forces than current instruments. This will be particularly useful for small biopsy samples or sorting for rare slow-growing tumor-initiating cells. In general, experiments performed in the Shared Resource are becoming more operator intensive, and the facility has reached the point where a second staff member is needed for sufficient capacity and optimal support for a diverse and growing base of users. Thus, partial salary support is requested for this technician. $109,057 in CCSG support is requested in the first year, representing 27.3% of the total annual operating budget of the Flow Cytometry Shared Resource.